Recent studies have demonstrated the potential for using a piezoelectric transduction device simultaneously for sensing and actuation. Due to the stability associated with collocated transduction devices in direct feedback control loops, concurrent use of the same device as a sensor and actuator has many applications. Piezoelectric transduction devices have been suggested for use in the suppression of flutter in panels, plate-like lifting surfaces as well as in airfoils. The transduction devices have also been considered for the suppression of interior noise within the fuselage of modern aircraft and for adding damping to flexible truss structures as required for large space structures.
The piezostructure, defined to be the combination of the structure and its surface mounted or embedded piezoelectric components, can be described by the second-order MDOF equation EQU Actuator Eqn. r+r+.OMEGA..sup.2 r=.THETA.v (1) EQU Sensor Eqn. q=.THETA..sup.T r+C.sub.p v (2)
where q is the piezoelectric's charge and v its voltage, r is in the natural (modal) basis of the structure, D describes the inherent damping, .OMEGA..sup.2 is a diagonal matrix of system eigenvalues, .THETA. is the electromechanical coupling matrix, and C.sub.p is the patch capacitance matrix. Thus, if the capacitance of the piezoelectric device is known, one must simply apply the same voltage across an "identical" capacitor and subtract the electrical response from that of the sensoriactuator to resolve the mechanical response of the structure.